\begin{tikzpicture}
    \draw (0,0) circle (1.2) node{$A$};
    \draw (1.8,0) circle (1.0) node{$B$};
    \draw (3.5,0) circle (1.3) node{$C$};
    \draw (-1.8, -2) rectangle (5.2,2);
    \node at (-1,1.6) {$I$};
\end{tikzpicture}
